Scanning processes are all around us. Images are generated for computer manipulation and enhancement almost as routinely as negatives are enlarged in a darkroom. Fax machines depend on scanning systems and the moving light "wands" of copiers can be easily seen scanning the original documents sequentially. Most electronic printers, offset printing presses, and 35mm camera focal-plane shutters scan their images. When we ourselves look at a large scene we normally scan the scene and construct a mental picture of the whole.
Scanning cameras that use traditional photographic products allow one to exploit the scanning imaging process for a wide range of applications including extreme wide-angle photography with pivoting lenses or cameras or photofinish photography or peripheral photography. I will describe below an application where a modified Polaroid pack-film type camera was used to make novel peripheral portraits.
In order to scan with film-type cameras one needs to simply restrict the field of view of the camera to a very narrow horizontal angle and then arrange for the film to simply move by behind this narrow vertical slit opening.
Since scanning means that one "stores" image information over time rather than gathering information about the whole subject simultaneously. Since in this "system" the film moves past an open slit, the film acts as "storage" or memory of events that occur on the slit over time.
Modifying the camera.
1. To modify a Polaroid camera that uses such films as Polaroid 667 or 668, or 665, you simply need to cover up the opening in the pack that delimits the image gate with a piece of opaque paper taped into the gate aperture. Leave only a slit-like opening at the end of the pack opposite the side where the white pull-tabs are located. Insert the pack in the camera.
2. Cover up the photocell of the camera with opaque black tape and then press on the shutter release. Keep the button depressed and the camera's shutter will open and remain open for a significant amount of time, maybe 10 seconds or so.
3. While the shutter is open pull out one of the white tabs steadily until the tab is completely removed. The film therefore will be exposed sequentially over time as it is moved past the open slit. It will effectively be scanning whatever moves across the slit in the pack. If the subject's image moves exactly at the speed at which the film is moving you should end up with a pretty realistic looking image of your subject.
Aiming the camera
Since the slit inside the camera is on the left side you need to make sure your subject passes by the right edge of your finder and moves from left to right. You can also photograph rotating subjects and with this process make 360 degree views of your subject. Just ask your subject to make a full turn during the time you pull the tab out of the camera. Make sure you subject remains lined up with the right edge of your finder.
If you have someone walk or run in front of the camera, the time it should take you to pull the white tab out of the camera should be roughly equal to the time it takes them to go across your viewfinder. For rotating subjects you should just make a test exposure and if the image that you get is too stretched out then next time slow the speed at which you pull the tab down. If compressed then sped it up. As you change the speed at which you pull the tab out of the camera that will also affect the exposure. The slower the film moves the greater the exposure.
This is a rough ASCII sketch of what a modified camera might look like and the location of the mask over the film pack.
_____ <- LENS - NO SHUTTER (diaphragm yes) ___/ \___ | \...../ | | | | | ___ FILM FACING LENS | | | MOVES LEFT FOR | | | EXPOSURE AND THEN | .____|___ SLIT | FACES RECEIVER SHEET | V | | FOR DEVELOPMENT STEP | |____________|____________ |----|- -------------------V------|-----| <- vertical lines indicate gate | .---------------<------<---------< .-|--- -> PULL WHITE TAB TO "SHOOT" |/ / | |\___________________________________/ | | ==================================== | |________________________________________|
At the last ATPI convention I used one of these modified Polaroid cameras of my own construction to photograph students as they were turned in front of the camera by a motorized turntable. In my camera the film was also pulled out of the pack by a motorized mechanism but for experimental purposes manual operation is quite sufficient. Just like for some purposes manual focus cameras may be better to learn with than auto-focus models.
Examples of the photographs made at the convention are attached below. If you would like further information about this novel photo-optical scanning technique please write to me, Andrew Davidhazy, Photographic Technology, Rochester Institute of Technology, PO Box 9887, Rochester, NY 14623 or send me e-mail at firstname.lastname@example.org